Liquid rheostat.



UNITED STATES PATENT OFFICE.

GEORGE H. DORGELOH, OF SGHENEGTADY, NEW YORK, ASSIGNOIR. TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

LIQUID RHEOSTAT.

Specification of Letters Patent.

Patented July 17, 1917.

To all whom it may concern:

Be it known that I, GEORGE H. DORGELOH, a citizen of'the United States, residing at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful Improvements in Liquid Rheostats, of which the following is a specification.

This invention relates to rheostats for controlling electric circuits, and especially to a form of liquid rheostat which will be found of peculiar advantage in the operation of induction motors having their rotor windings terminating in collector rings which are to be connected to outside resistances. In this class of work it is desirable to have as great a range of resistance as possible between the starting and running positions of the rheostat and to reduce the final resistance as low. as possible in order to minimize the slip of the motor at full load One point of weakness in all liquid rheostats heretofore devised has been the low range of resistance, or, in other words, the low ratio between the initial and the final resistance values. This defect has been due largely to the fact that the electrodes or plates must be spaced so far apart to avoid flashing over at high voltage that a low final resistance could not be obtained.

My invention aims to overcome the difficulty by having in addition to the main electrodes a set of auxiliary electrodes which are more closely spaced than the main electrodes and connected in parallel with the main electrodes but are notimmersed until the resistance has been reduced. They are therefore out of circuit at starting and there is no danger of arcing due to the close spacing. These auxiliary electrodes are separated from the liquid by a wall which may surround them so as to constitute a chamber which is separate from the main chamber. This prevents the vapor which rises from the liquid before the auxiliary electrodes are immersed from coming into contact wlth the auxiliary electrodes and causing leakage or flash over between them. This auxiliary chamber is connected with the main chamher so that the liquid will flow into it at the proper time and immerse the auxiliary electrodes. With this arrangement there is a low final resistance due to closely spaced electrodes without danger of flashing over during the early stages of starting because of the close spacing.

The accompanying drawing shows an embodiment of my invention, Figure 1 being a diagram of the electrical circuits, and Fig. 2 a diagrammatic section of the water tank and its two electrode chambers.

The motor M to be controlled is an induction motor having its rotor windings connected to slip rings 1 which are connected by conductors 2 to a set of main electrodes or plates 3 and a set of auxiliary electrodes 4: all inclosed in a tank R. The two sets of electrodes are separated by a wall or partition 8 which virtually forms a separate chamber for the auxiliary electrodes The two sets of plates are connected in multiple and those in chamber 5 are few in number and of large size, being long enough to dip below the lowest water level at all times. The plates 4 are more in number than the plates 3 and more closely spaced, and their lower ends are at a higher level than those of the plates 3, so that they hang well above the water at starting. The two chambers are connected by the orifice 7 in the partition 8 which separates them, so that the water level is always the same in both chambers, and there is a free path for the electric current through the liquid from the plates in one chamber to those in the other.

In one end of the chambers is an opening, the height of whose sill 9 above the bottom of the chamber determines the depth of the liquid therein at starting. This opening is controlled by a gate or weir 10, preferably carried on rock arms 11 pivoted at 12 and capable of oscillation by an arm 13, link 14:, and pivoted lever 15. A sector gear 16 on the hub of the lever meshes with a pinion 17 on the shaft of a controller G. Then the lever is thrown over to turn on the current, it also lifts the weir, which causes a rise of the water level in the chambers 5 and 6.

A pump P driven by an electric motor M takes liquid from the tank R and delivers it constantly to the chambers 5, 6, the overflow running back into the tank, so that the vapor arising fromthe liquid wlll be preliquid is. continuously circulated, and the heat is kept down.

Current is supplied to the three-phase motor from leads a, 0, two of which are controllecbby contactors 18, 19, each provided with an interlock 20, 21 controlling the circuit of the other.

When the controller C is turned to the firstforward position 7 and theswitch S is closed, the winding of the contactor 18 will be energized by current flowing from the phasea through the contacts on the controller and the interlock 21 on the c'ontactor 19',"andb'ack" to phase Z); This will "close the'p'rimary circuit of the "motor M, "and since there is some liquid in the bottomof the chamber 5 the secondary circuit will be completed through the 'high resistance afforded by the widely spaced long plates 3,

and" the motor will start. The steam or vented fro ncoming into contact with the auxiliary electrodes and causing a leakage or flash over bythe partition or wall '8. "At the same time that the controller is operated, the weir will be lifted. The closing of the "switch 5 also causes the motorM to start the pump P to forcing liquid into the Water chambers. As theliquid rises 'thereinthe resistance in the secondary circhit of the motor will" decrease until the liquid reaches-a height determined by the position of the upper edge of the weir, over which it,then flows to the" tank. For the first position of the controller, theweir stands at such a" height that the liquid does hot wet the auxiliary plates 4. But when the controller-Ts thrown over to the position '1, theweir is raised so high that the liquid immers'es the plates 1, and since theyare connected inparallel with the plates- 3 and are set more closely together,t he resistance is greatly lowered. When thtewvatenre'aches its highest level, the resistance is'much lower than it could be with the plates 3 alone. In

like manner, if the controller is thrown to the opposite'position 7', the contactor 1Q will be'energized to reverse the motor, andi'n the 'final position 1 of the controller the plates 41- willbe thrownin parallel with the plates 3 as before.

"Inthe"normal operation of my device, in controlling a collector ring induction motor fordriving'a hoist, for example, the switch S will be kept'closed, sotha tthe pump P will continuously circulate water between thetankR andthe'water chambers 5, 6." It is therefor'e only necessary to move the bandle inonedirection or the other toefi'ec't the starting of the motor either forward or backward. When theincr'easing speed of the"motor has caused the voltage to drop sufficiently to permit a closeiflspacing of the plates, the handle is moved to the final positio n to cause the liquid to immerse the plates '45. As the liquid rises, resistance gradually lowers, until at the highest level of we liqui he na re i anc s e y themotbr gets practically full line voltage, and the loss due to the slip of the rotor is almost ail. Inac'cordance with the provisions of the patent statutes, I have described the principleof operation of my invention together withtheapparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood thatthe apparatus shown is only illustrative, and that the invention can" be carried" out by other means.

' l'claim as-newand desire to secure by Letters Patent-'oif'thelln ited States is "1. A liquid The'stat for electr-ic circuits, comprising two connected chambers, two sets of electrodes in parallel with each other one i11"-eac11 chamber, and means for 1111- comprising two connected chambers, a setof widely spaced electrodes in one chamber, a set'of more closely spaced electrodes in the other chamber, and "means for immersing said 'sets' 'siicc-essively. 4i A liquid rheostat for electric-circuits, comprising two connected chambers, a set of widely spaced electrodes in one chamber, aset of more closelyspaced electrodes the other chamber, thelower ends of the second set being at a hi-gher level than those of the first set, andmeans for raising the level of the"liquid in both chambers.

liquid rheostatcomprising a tank, main electrodes and auxiliary electrodes more closely spaced arranged to be successiv'ely immersed in said tank and means for -preventing thevaporrising from theliquid when the main electrodes are immersed from coming into contact with the auxiliaryelectrodes; I 6. A liquid rheostat for electric circuits "comprising main electrodes, auxiliary electrodes more closely spaced than the main electrodes and normally connected in-parallel therewith, a separatingwall between the main and auxiliary electrodes, and means for immersing the auxiliary" electrodes atter the resistance has been reduced at the main electrodes;

7. A liquid rheostat'for electric circuits comprisinginain' "electrodes, auxiliary electrodes more closely spaced than the main electrodes and normally connected in par- In witness whereof, I have hereunto set allel therewith, a wall for protecting the my hand this 29th day of July, 1914. auxiliary electrodes from vapor generated at the main electrodes and means whereby GEORGE DORGELOH' the auxiliary electrodes are immersed after Witnesses:

the resistance has been reduced at the main BENJAMIN B. HULL,

electrodes. HELEN ORFORD.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. G. 

